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Adrenergic Agonists and Antagonists > Adrenergic Agonists and Antagonists > Flashcards

Adrenergic Agonists and Antagonists Flashcards

1
Q

Gq receptor

A
  • alpha 1
  • phospholipase C hydrolyzes PIP2
  • increased intracellular calcium
  • calcium dependent protein kinases
  • protein kinase C activated
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2
Q

Gi receptor

A
  • alpha 2
  • down regulated adenylyl cyclase
  • decreased cAMP
  • decreased protein kinase A
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3
Q

Gs receptor

A
  • beta 1, 2, and 3
  • upregulates adenylyl cyclase
  • increases intracellular cAMP
  • increases protein kinase A
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4
Q

antagonists

A

bind inside the 7 alpha helix transmembrane protein… bind inside the membrane

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5
Q

Direct Acting

A
  • alpha agonists (nonselective, a1 selective, a2 selective)

- beta agonists (nonselective, b1 selective, b2 selective)

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6
Q

Indirect Acting

A
  • releasers (increase in norepi or epi)

- reuptake inhibitors (induce release of catecholamines by inhibiting reuptake of norepinephrine)

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7
Q

Epinephrine

A
  • catecholamine
  • direct adrenergic agonist
  • alpha1=alpha2
  • beta1=beta2
  • increase in drying of cutaneous, mucous membranes (alpha)
  • large increase in contractility
  • increase in systolic pressure
  • increase or decrease in diastolic
  • increase in pulse pressure
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8
Q

Norepinephrine

A
  • catecholamine
  • direct adrenergic agonist
  • alpha1=alpha2
  • beta1»beta2
  • used (uncommonly) for pressor effects
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9
Q

Isoproterenol

A
  • catecholamine
  • direct adrenergic agonist
  • beta1=beta2»»alpha
  • decrease in drying of cutaneous, mucous membranes (alpha)
  • decrease in total peripheral resistance
  • large increase in contractility
  • large increase in heart rate
  • large increase in CO
  • decrease in diastolic pressure
  • little decrease or no change in systolic pressure
  • increase in pulse pressure
  • used (uncommonly) for bronchodilation (but largely superseeded by beta2-selective agonists)
  • used for heart stimulation in bradycardia or heart block (direct + reflex from beta2 effects)
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10
Q

Dobutamine

A
  • catecholamine
  • direct adrenergic agonist
  • beta1>beta2»»alpha
  • positive inotropic effects more prominent than (+) chronotropic effects, used in congestive heart failure (acute)
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11
Q

Dopamine

A
  • catecholamine
  • direct adrenergic agonist
  • D1=D2»beta1»alpha
  • important because at high doses it can have other effects due to its binding at beta-1 and alpha
  • D1 response: vasodilation of renal, mesenteric, and coronary beds
  • careful monitoring (severe vasoconstriction (no beta2), ischemia of peripheral tissues)
  • used for heart stimulation with positive effects on renal output
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12
Q

Phenylephrine

A
  • nonchatecholamine
  • direct adrenergic agonist
  • alpha1>alpha2»»>beta
  • increase in drying of cutaneous, mucous membranes (alpha)
  • splanchnic (alpha)
  • big increase in total peripheral resistance
  • decrease heart rate (vagal reflex)
  • increase in diastolic and systolic pressures
  • vasoconstrictive effects used to treat hypotension, shock
  • also used in nasal congestion (topical), ophthalmic effect (topical) - mydriasis
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13
Q

Clonidine

A
  • nonchatecholamine
  • direct adrenergic agonist
  • alpha2>alpha1»»beta
  • penetrates CNS, inhibits sympathetic output and produces hypotension, bradycardia, and sedation
  • used in hypertension
  • diminishes craving in narcotic, alcohol, and nicotine withdrawal
  • withdrawal from clonidine causes reflex hypertension (treated with phentolamine)
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14
Q

Albuterol, ritodrine

A
  • nonchatecholamine
  • direct adrenergic agonist
  • beta2»beta1»»alpha
  • used in asthma and COPD for bronchodilation
  • inhalers minimize systemic effects
  • can be used as uterine muscle relaxant to delay preterm labor (benefits?)
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15
Q

Amphetamine, methylphenidate

A
  • nonchatecholamine
  • indirect adrenergic agonist (alpha&beta, typically like norepinephrine)
  • readily enters CNS and releases catecholamines including dopamine and norepinephrine
  • CNS: elevates mood and alertness, suppresses appetite
  • used in narcolepsy, weight loss, ADHD (methylphenidate)
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16
Q

Tyramine (when MAO inhibitor present)

A
  • nonchatecholamine
  • indirect adrenergic agonist (alpha&beta, typically like norepinephrine)
  • in food
  • important if MAO inhibitor present, produces NE-like hypertensive response
  • if MAO inhibitor is present then tyramine is not metabolized and leads to the hypertensive response
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17
Q

Cocaine

A
  • nonchatecholamine
  • indirect adrenergic agonist (alpha&beta, typically like norepinephrine)
  • blocks the reuptake of norepinephrine
  • vasoconstriction + local anesthetic
  • abuse side effects include hypertensive response
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18
Q

Ephedrine

A
  • nonchatecholamine
  • mixed adrenergic agonist (indirect plus direct alpha&beta)
  • some CNS penetration, mild stimulent
  • orally available, excreted unchanged
  • long duration of action
  • used as nasal decongestant, bronchodilator (cold medications)
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19
Q

Pseudoephedrine

A
  • nonchatecholamine
  • mixed adrenergic agonist (indirect plus direct alpha&beta)
  • some CNS penetration, mild stimulent
  • orally available, excreted unchanged
  • long duration of action
  • used as nasal decongestant, bronchodilator (cold medications)
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20
Q

Therapeutic Uses of Epinephrine

A
  • anaphylactic shock (bronchoconstriction, hypotension, vascular collapse, angioedema (alpha and beta)
  • acute asthma attacks (beta) (now have drugs more specific for beta2)
  • prolong action of local anesthetics (alpha)
  • topical hemostatic agent (alpha)
  • cardiac arrest (alpha - increase diastolic pressure, improve coronary and cerebral perfusion)
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21
Q

Adverse Effects of Epinephrine

A
  • special precautions in hyperthyroid patients and patients on beta-blockers
  • marked hypertension
  • arrhythmias
  • angina
  • necrosis following extravasiation
22
Q

Dose Dependency on Dopamine

A
  • 0.5-2.0 = D1 effect
  • 2-10 = beta1 effect
  • > 10 = alpha effect
23
Q

Nonspecific Alpha Blockers (alpha1 + alpha2)

A
  • predominant effect is vasodilation
  • reflex tachycardia potentiated by decreased alpha2-mediated feedback inhibition (alpha2 receptors on nerve terminal, inhibit feedback inhibition)
  • hypotensive response blunted by increased cardiac output (BP = CO x PVR)
  • adverse effects follow actions: orthostatic hypotension, nasal stuffiness, tachycardia
24
Q

Phenoxybenzamine

A
  • nonspecific alpha blocker
  • given PO
  • requires bioactivation (lag in onset), covalent, irreversible (>24 hour duration)
  • used for treatment of pheochromocytoma
25
Q

Pheochromocytoma

A
  • tumor of the adrenal medulla in the area where norepinephrine is synthesized
  • huge increase in norepinephrine due to tumor growth
26
Q

Phentolamine

A
  • nonspecific alpha blocker
  • competitive (shorter duration)
  • given IV
  • used for short term treatment of pheochromocytoma, iatrogenic alpha-agonist reversal and for hypertensive crisis (abrupt clonidine withdrawal, tyramine + MAO inhibitor)
27
Q

alpha1 Blockers (alpha1»»alpha2)

A
  • decrease blood pressure with less reflex stimulation of heart rate (because alpha2 is not blocked as much)
  • decreases preload and afterload
  • used to treat hypertension (first dose produces orthostatic hypotension then tolerance)
  • relaxation of smooth muscle in prostate, urethra, and bladder neck
  • used to promote urine flow (benign prostatic hyperplasia) with or without 5(alpha)-reductase inhibitor
28
Q

Prazosin

A
  • alpha1 blocker

- hypertension and BPH

29
Q

Terazosin

A
  • alpha1 blocker

- hypertension and BPH

30
Q

Tamsulosin

A
  • alpha1 blocker
  • some selectivity for alpha1-A receptors
  • claimed to promote urine flow in BPH with little effects on blood pressure
31
Q

Effects of Beta Blockers: CV

A
  • decrease myocardial contractility (most evident following exercise and stress)
  • decrease heart rate
  • short term: decrease CO, increase peripheral resistance (beta2 blockage)
  • long term: peripheral resistance normalizes (net effect: decrease myocardial O2 consumption)
32
Q

Effects of Beta Blockers: Blood Pressure

A

-no effect on normals, decrease hypertension in hypertensives

33
Q

Effects of Beta Blockers: Pulmonary

A
  • beta2 antagonism of bronchodilation

- dangerous in COPD and asthma

34
Q

Effects of Beta Blockers: Eye

A

-decreases aqueous humor production from ciliary epithelium

35
Q

Effects of Beta Blockers: Metabolic

A
  • blocks glucose mobilization (beta2 antagonism of glycogenolysis)
  • slows lipolysis, increases VLDL, lowers HDL (unfavorable… mechanism unclear)
36
Q

beta1>beta2

A

-cardioselective (less effects on lung), not absolute

37
Q

partial agonist activity of beta blockers

A
  • intrinsic sympathomimetic activity, ISA

- possibly useful for patients who develop symptomatic bradycardia or asthma with pure antagonists

38
Q

local anesthetic properties of beta blockers

A
  • “membrane stabilizing activity”, MSA

- undesirable when used topically on the eye

39
Q

Pharmacokinetics of Beta Blockers

A
  • most well absorbed after oral administration
  • bioavailability, first pass metabolism, and clearance depend on agent
  • duration of action: typically hours (exception is Esmolol, which is hydrolyzed by erythrocyte esterase with a half-life of ~10 min… so tight control and used IV)
40
Q

Therapeutic Uses of Beta Blockers

A
  • angina (improves exercise tolerance, decreases cardiac O2 consumption) - not agents with ISA
  • hypertension
  • SVT and ventricular arrhythmias
  • myocardial infarction (immediately after and prophylactically) - not agents with ISA
  • hyperthyroidism (counteracts beta-receptor up-regulation) - thyroid storm
  • glaucoma (decreased production of aqueous humor… decreases pressure in eye caused by glaucoma) (MSA problematic)
  • neurological: migraine (prophylactic); tremor
  • heart failure!! (carvedilol, others, clinical trials)
41
Q

Adverse Effects/Contraindications of Beta Blockers

A
  • heart failure (counteracts sympathetic compensation)
  • bradycardia (ISA may help)
  • COPD and asthma (beta1-selectivity may help but not absolute)
  • abrupt withdrawal can lead to angina, sudden death (enhanced beta sensitivity)
  • blunt recovery from hypoglycemia, also mask symptoms (of concern in insulin-dependent diabetics)(beta1-selectivity may help)
  • adverse plasma lipoprotein profiles (ISA may help)
  • CNS effects (sleep disturbances, depression) (lower lipid solubility may help)
42
Q

Propranolol

A
  • nonselective beta blocker
  • no ISA
  • yes MSA
  • high lipid solubility
  • prototypic agent!
43
Q

ISA

A
  • intrinsic sympathomimetic activity
  • beta blockers that show both agonism and antagonism at a given beta receptor depending on concentration of the agent (beta blocker) and the antagonized agent (usually endogenous like norepinephrine)
44
Q

MSA

A
  • membrane stabilizing activity
  • involve the inhibition or total abolishing of action potentials from being propagated across the membrane
  • phenomenon is common in nerve tissues as they are the carrier of impulses from the periphery to the central nervous system
  • method through which local anesthetics work
45
Q

Esmolol

A
  • beta1-selective beta blocker
  • no ISA
  • no MSA
  • low lipid solubility
  • given IV
  • short half-life (~10 min)
46
Q

Acebutolol

A
  • beta1-selective beta blocker
  • yes ISA
  • yes MSA
  • low lipid solubility
47
Q

Carvedilol

A
  • nonselective beta blocker
  • no ISA
  • no MSA
  • unknown lipid solubility
  • some alpha1 blockage
48
Q

Pindolol

A
  • nonselective beta blocker
  • yes ISA
  • yes MSA
  • moderate lipid solubility
49
Q

Atenolol

A
  • beta1-selective beta blocker
  • no ISA
  • no MSA
  • low lipid solubility
50
Q

Timolol

A
  • nonselective beta blocker
  • no ISA
  • no MSA
  • moderate lipid solubility

Adrenergic Agonists and Antagonists (1 decks)

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